Vapor electric converter



Aug. 9, 1938. J, SLEPIAN 2,126,291

7 VAPOR ELECTRIC CONVERTER Filed March 24, 1937 WITNESSES Y .Zoseph S/ep/bn.

ATORNEY Patented Aug. 9, 1938 warren srnrss VAPOR ELECTRIC CONVERTER Joseph Slepian, Pittsburgh, Pa, assignor to Westinghouse Electric & Manufacturing Company,

East Pittsburgh, Pa,

sylvania Application March 24,

. 8 Claims.

My invention relates to a vapor electric converter and particularly to an ignition system for such a converter.

In the operation of vapor electric converters having a make-alive type of excitation, it has been found that there is considerable delay inthe formation of the rectifying arc to the anode. This delay has been particularly noted in regard to the high resistance low current type of igniter, sometimes being of the order of several thousand micro-seconds. By observation of the operation of these devices, I believe that this effect results because the startingcurrent arc does not produce sufiicient vapor for the quick transfer of the arc to the main electrodes.

Another trouble met with in converters of this type is that liquid mercury may condense or be thrown upon the igniter electrode and stick there. This condensed mercury causes a large increase in the current required by the igniter for starting the arc.

According to my invention, this delay in starting may be eliminated and the sticking of mercury to the igniter prevented byapplying heat to When the heating current is passed through the auxiliary electrode, it has been noted that a current much smaller than the current which will regularly produce a cathode spot will occasionally cause a random occurrence of a cathode spot. I believe that this random occurrence is caused by the heating current producing sufficient vapor pressure to push the cathode material away from contact with the auxiliary electrode and thus create a spark which initiates the cathode spot. I have found that this random occurrence can be prevented by suitably cooling the end of the make-alive electrode in contact with the cathode material or by having the end of the make-alive electrode in permanent electrical contact with a highly conducting element which is in permanent electrical contact with the cathode material. While this cooling may be done by immersing the make-alive electrode a suitable depth into the a corporation of Penn- 1937, Serial No. 132,830

the material of the cathode. Since this block of metal remains permanently in contact with the cathode material, the heater circuit is never broken.

Another method of preventing the heating circuit from being interrupted by motion of the cathode material, .is to provide two terminals to the make-alive electrode for the flow of heating current, which are independent of the cathode material. This may be done by making the makealive electrode of hairpin form.

Other objects and advantages of my invention will be apparent. from the following detailed description taken in conjunction with the accompanying drawing, in which:

Fig- 1 is a schematic illustration of a converter embodying my invention;

Fig. 2 is a similar view of a converter embocly ing an independent heater; 7

Fig. 3 is a modification similar to Fig. 1, but having an independent sourceof excitation;

Fig. 4 is a further modification showing the use of an independent heater element; and

Fig. 5 is a modification showing a hairpin type of make-alive electrode.

The construction according to my invention is a simple arc chamber I having a single anode 2 and a cathode 3 with a make-alive electrode 4 supplied from the anode circuit 5 by a suitable uni-directional conductor, such as a glow tube 6. In normal operation of my device, the glowtube 5 will break downupon the application of positive potential'to the anode 2 and passes starting current to the make-alive electrode i, which initiates a cathode spot, which in turn strikes the main arc and short circuits the glow tube 6 removing current from the make-alive electrode.

To this simple converter I add a heating circuit by placing in shunt with the glow tube a resistance it which allows a continuous heating current to flow through the makealive electrode. This resistance iii should be of such a value that the heating current is well below the value of current necessary to initiate a cathode spot.

In order to prevent unnecessary heating of that portion of the electrode 4 in contact with the. cathode material 3, I provide the make-alive electrode with a suitable cooling element in the form of a metallic block i l attached to the electrode and immersed in the cathode material 3.

In the modification according to Fig. 2, the heating of the auxiliary electrode i is accomplished by means of a heating coil l5 supplied from a suitable source of current, such as a transformer l6.

In the modification according to Fig. 3, the excitation or ignition current for the converter is applied to the make-alive electrode 4 from a suitable source, such as a transformer 20, through a grid-controlled discharge device 2|, the grid of which is controlled bythe potential applied to the anode 2 of the converter. The auxiliary discharge tube is by-passed by a suitable resistance IE! for providing heating current to the makealive electrode 4.

In the modification according to Fig. 4 the make-alive current is controlled by a commutating device 25 driven by a suitable motor 26 preferably a synchronous motor. In order to prevent sparking at the commutator I provide a suitable capacitor 21 bridging the contacts. A resistor 28 of proper capacity may be placed in parallel with the capacitor 2'! to pass heating current through the electrode 4. By properly proportioning resistors l and 28 the heating effect may be divided between the heater coil l and the heating current passing through the electrode 4. While the return connection from the coil l5 to the current source 29 may be made in any preferred way I prefer to connect the coil directly to the cathode 3 and protect it from the arc by a suitable insulating sleeve 30 in order to reduce the number of vacuum seals required.

In the modification according to Fig. 5 a hair pin type of make-alive electrode is utilized comprizing two make-alive elements connected together by means of the cooling block II. A suitable heating current is circulated through the make-alive electrodes from any suitable source such as a heating transformer 35. The makealive current from anode connection 5 is supplied by discharge device 6 preferably to a mid tap on the secondary winding of transformer 35.

In the operation of these devices whether the current is supplied directly to the auxiliary electrode or to an independent heating element l5 associated therewith, the heating current produces a continual evaporation of the material adjacent to the auxiliary electrode, and consequently maintains a vapor pressure in the vicinity of the auxiliary electrode 4. Also by maintaining the auxiliary electrode at a relatively high temperature, it prevents condensation of the cathode material on the surface of the auxiliary electrode.

While I have shown and described specific embodiments of my invention, it will be apparent to those skilled in the art that many modifications can be made therein without departing from the true spirit of my invention by the scope of the appended claims.

I claim as my invention:

1. A vapor-electric converter comprising an arc-chamber, a pair of main electrodes therein, at least one of said electrodes being of vaporizable material, a make-alive electrode having a portion thereof immersed in said vaporizable electrode, means responsive to the polarity of the potential impressed on the main electrodes for impressing make-alive current on said make-alive electrode, a resistance in shunt with said means for impressing a lesser current on said make-alive electrode and means for cooling the portion of the makealive electrode immersed in the vaporizable cathode.

2. A vapor-electric converter comprising an arc chamber, a plurality of main electrodes in said chamber, one of said main electrodes being of vaporizable material, a make-alive electrode in contact with said vaporizable electrode, means for periodically passing make-alive current through said make-alive electrode, and means for continuously passing a lesser current through said make-alive electrode.

3. A vapor-electric converter comprising an arc chamber, a plurality of main electrodes in said chamber, one of said main electrodes being of vaporizable material, a make-alive electrode in contact with said vaporizable electrode, means for periodically passing make-alive current through said make-alive electrode, means for continuously passing a lesser current through said make-alive electrode, and means for preventing said lesser current from accidentally creating a cathode spot on said vaporizable electrode.

4.. An ignition system for a vapor-electric device comprising an ignition electrode in contact with the cathode of the device, a source of potential for said electrode, a uni-directional conductor for passing igniting current to said electrode, and means for heating the ignition electrode.

5. An ignition system for a vapor-electric device comprising an ignition electrode in contact with the cathode of the device, a source of potential for said electrode, a unidirectional conductor for passing igniting current to said electrode, and means for maintaining a vapor pressure in the vicinity of the ignition electrode.

6. A make-alive system for a vapor-electric converter comprising a make-alive electrode in contact with the cathode material of said converter, a source of potential for supplying current to said make-alive, means for interrupting the make-alive current and means for continuously supplying a heating current to said makealive.

7. An ignition system for a vapor-electric converter having an arc-chamber and a plurality of main electrodes therein, comprising an auxiliary electrode having a portion thereof immersed in one of said main electrodes, a source of potential for said auxiliary electrode, means for intermittently applying said potential to said auxiliary electrode and means for heating said auxiliary electrode.

8. An ignition system for a vapor-electric converter having an arc-chamber and a plurality of main electrodes therein, comprising an auxiliary electrode having a portion thereof in contact with one of the main electrodes, a connection with the main electrode supply circuit for supplying current to said auxiliary electrode, means in said circuit for interrupting the current to said auxiliary electrode and means for by-passing current around said interrupting means for heating the auxiliary electrode.

JOSEPH SLEPIAN. 

